1. Field of the Invention
The present invention relates to a packet processing method using a multiple fault tolerant network structure, in particular to a packet processing method using a multiple fault tolerant network structure which is capable of performing communication of a whole ring and disusing a useless packet when a fault occurs on a plurality of connection lines and nodes by using a dual ring structure.
2. Description of the Prior Art
In general, a large scale system is constructed as modules by functions, and a connection network is used in order to connect the each module. When a fault occurs on the connection network, the system can not perform normal operation. For example, a distribution system constructed with connected computers may not operate normally due to the fault.
Among network structures for overcoming the fault problem of the connection network, a ring structure can efficiently connect scattered nodes with minimum connection lines on the comparison with connection lines of a star network and a mesh network.
However, in the ring structure, when the fault occurs on the one node or one connection line, the communication between the all nodes is disconnected. Accordingly, in order to prevent it a dual connection network is used in a system required a high credibility.
FIGS. 1a and 2a illustrate the conventional dual ring structure, the dual ring of FIG. 1a connects the each node 10, 11, 12, 13 to a different direction each other, the dual ring of FIG. 2a connects the each node 20, 21, 22, 23 to the same direction. In other words, FIGS. 1a and 2a illustrate the structure of the conventional duplicated FDDI (Fiber Distributed Data Interface) connection network, the FDDI is constructed with the duplicated connection network, when the fault occurs on a certain node, the rest of the nodes are reconstructed with single connection network, accordingly the nodes which doesn't have the fault occurrence can perform communication normally.
FIG. 1a illustrates a ring structure which prevents the communication cut off between the nodes when the fault occurs on the one node or the one connection line by constructing the rest of the nodes as a single ring. FIG. 1b illustrates the delayed state of the dual ring structure of FIG. 1a in the fault occurrence, in more detail when the fault occurs on a node 3 12, the node 3 12 forms a single ring by detouring a packet to each connection line b1, b2 in order to perform the communication continually. However, when the conventional dual ring is reconstructed as the single ring due to the fault occurrence and a fault occurs again on the other node or connection line, the overall system can not operate normally.
FIGS. 2a and 2c are represented in order to solve the above-mentioned problem. In FIG. 2a, the each node selects one good signal between two inputs, and it transmits the input as two outputs at the same time when its node is not an object node in order to make the communication perform when the fault occurs a plurality of the connection lines or even the fault occurs on the one connection line of the each node. In FIG. 2a, when the fault occurs on a connection line L1, a connection line L2 makes the communication possible.
FIG. 2c illustrates communication system represented in the Japan patent official bulletin No. 60-169255 (Patent date. Sep. 2, 1985), the each node receives same two inputs, transmits same two outputs, when the fault occurs on the one connection line, the node does not receive a packet from the fault occurred connection line, but receives a packet from the other connection line. In other words, in FIG. 2d, when the fault occurs on the connection line L1, a node 21 receives an input packet of a reception line R′ on the behalf of a reception line R, accordingly the communication is possible. However, as depicted in FIGS. 2b and 2e, when the fault occurs on the more than one node, the overall communication is cut off.
FIG. 3a is a construction profile illustrating the conventional dual ring cross path, the conventional technology related to it is represented in the Korea patent No. 0123064 (Patent Registration Date Sep. 10, 1997). In the dual ring cross path, two duplication transmission/reception interface devices 30, 31 pass through each connection line, 4 packets are transferred between nodes through 4 paths in order to make the one packet arrive the final object node. Herein, when the fault occurs on two D-nodes (for example, 302 and 312), the communication is cut off due to an island occurrence.
FIG. 3b illustrates a high speed data transmission represented in the U.S. Pat. No. 4,837,856 (Patent Registration Date. Jun. 6, 1989) and a fault tolerance fiber optic sense connection line/tandem line for being used in a similar field. In the patent, the signal transmission is performed by comprising a primary line and at least one bypass line, analyzing signals from the lines, comparing them with a preset value, and selecting one among them. In the patent, when the packet is transmitted from a node 351 to a node 354, the packet starts from the node 351 and is received to the node 353, the node 353 transmits the packet to the node 354 and 355. When the fault occurs on a connection line L1, the node 355 receives the packet to be disused from the node 353, the packet is outputted to the connection line L3, L4, the useless packet continually uses the ring, accordingly it causes the communication difficulty.